1. Field of the Invention
The present invention relates to a coiled optical assembly made of a long optical fiber and a fabricating method for the same; and, in particular, to a dispersion compensator for reducing the wavelength dispersion of an optical fiber transmission line in the wavelength band of 1.55 μm, and a fabricating method for the same.
2. Related Background Art
Long-distance, large-capacity transmission is possible in the wavelength band of 1.55 μm by means of an optical amplifier operable in the wavelength band of 1.55 μm utilizing an optical fiber doped with erbium (Er) which is a rare-earth element. However, when transmission is carried out in the wavelength band of 1.55 μm by using a single-mode optical fiber whose zero-dispersion wavelength is in the 1.3-μm band (1.3 SMF), which is employed in conventional optical transmission lines, then a large wavelength dispersion occurs and distorts optical signals, thereby deteriorating the signal quality. As a consequence, when carrying out transmission in the 1.55-μm band with the use of 1.3 SMF, its wavelength dispersion is required to be kept low. Known as one of techniques therefor is a method using a dispersion-compensating optical fiber (DCF) having a large wavelength dispersion with a polarity opposite to that of the dispersion of 1.3 SMF, so as to cancel the wavelength dispersion in the 1.55-μm band.
In a technique employed for carrying out such dispersion compensation with DCF in a conventional long-distance transmission line, a dispersion compensator having a compact size in which a long DCF is wound around a bobbin is installed at every repeater station.